Current spray atomizers employed in coating a workpiece have several drawbacks which impair their ability to transfer the atomized coating to the workpiece. These include, but are not limited to, a loss of energy as the atomized particle travels from the spray device to the workpiece, overspray, errant particles of multiple sizes, and a bounce-back effect from the workpiece.
When a pattern of coating leaves a spraying device it passes through several stages. The first stage is the atomization of the coating, the second stage is the shaping of a of a spray pattern, such as a fan pattern, by pattern shaping devices located on the front portion of the spraying device. The atomization of the coating does not produce a plethora of uniform coating particle sizes, but a distribution of larger sized coating particles, medium sized coating particles, all the way to micron sized coating particles. After the atomized coating has left the region proximal the nozzle and moves toward the workpiece, the coating experiences the effect of decompression, which causes a portion of the atomized particles of the coating to stray from the main pattern and become errant. These errant coating particles are very small and are not affected by gravity, they literally float in the air proximal the spray. This decompression region in the spray pattern is problematic in that it includes particles that are less than 10 microns in size. Without safety measures a particle of such a size can easily infiltrate the lungs and be retained therein. Due to the nature of many coatings, be they toxic or non-toxic, the infiltration of such particles into the lung is highly undesirable. Although the compressed air is the primary driver of the coating to the workpiece, it is also this pressure which causes the decompression which in turn is one of the major factors in the creation of overspray. As the coating travels farther from the nozzle toward the workpiece, the energy of the pattern begins to lose it's frictional bond and deplete. When the coating reaches the target workpiece, it experiences bounce-back when over-energized or not controlled by some other means.
In the process described, the percentage of the coating that it actually delivered to the workpiece, known as Transfer Efficiency (TE) is relatively low. The closer the nozzle is to the workpiece, a higher transfer efficiency (TE) may be achieved; however, this must be done with the appropriate amount of energy moving the atomized coating particles through the atmosphere between the spray device and the workpiece. At a constant air pressure moving the atomized coating, if the nozzle is too close to the workpiece, it will cause more bounce back as well as running of the coating on the workpiece. Alternatively, if the nozzle is too far away from the workpiece, insufficient atomized coating will be able to travel the distance. Both of these scenarios have a negative impact on the transfer efficiency as well as the quality of the coating on the workpiece.
A skilled and experienced operator would find a sweet spot for maximum transfer efficiency, by adjusting the distance of the spray device to the workpiece, adjusting the level of pressurized air moving the atomized coating toward the workpiece, as well as other tricks of the trade. However, even at this sweet spot, the generation of overspray, microscopic errant particles, bounce-back and other factors give an upper limit to the transfer efficiency. Over 50% of material sprayed by a spray device is lost to the above named factors combined with other factors. Even if the overspray is collected and the errant particles corralled, it may help the environment but does not put any more coating on the workpiece.
What is required is a device which will energize the coating particles in the spray pattern leaving the spray device while in flight to the workpiece, this additional energy coming in the form of a controlled pattern of additional compressed air. This additional compressed air would come from an attachment which would mount on the front portion of the spray device. The attachment would have a second supply of compressed air which would enter an air hub. Depending from the outer sidewall of the air hub are four (4) vanes which are located about 90° to each other. Two of these vanes have a first length and two of these vanes have a second length.
Insofar as this invention is concerned, compressed air is not limited solely to compressed atmospheric air. Below follows a list of the mixture of gases which are found in atmospheric air.
Components of Atmospheric Air by Molar Percent
Nitrogen78.084%Oxygen20.994%Argon0.934%Carbon Dioxide0.035%Neon0.001818%Helium0.000524%Methane0.00017%Krypton0.000114%Hydrogen0.000053%Nitrous Oxide0.000031%
In addition Ozone, Carbon Monoxide, Sulfur Dioxide and Ammonia are present in atmospheric air in trace quantities.
It has been considered that the instant invention may be utilized with gasses or combination of gasses which are different than atmospheric air. These gasses and mixtures of gasses are would be compressed and utilized just as compressed air would be. In this application, the term compressed air includes compressed gasses and mixtures of gasses. Further, the term air in this application includes gas or mixture of gasses. For simplicity, the airhub 60 will allow the flow of not just air, but any gas, mixture of gas or microscopic elements which may be entrained therein. It will not be referred to as the gashub, rather as an airhub. The same follows for air passageways and air conduits.
All four of the vanes have an internal air passageway which permits the secondary compressed air to flow to the distal end of each of the four vanes. At the distal end of each of the four vanes, is a canted or angled vane element which also includes an internal compressed air passageway therein which is in communication with the internal air passageway of the four vanes. The distal end of each of the four vanes are canted or angled toward the workpiece. The secondary compressed air passageway which is located in the canted or angled portion of the four vanes each have a secondary compressed air exit, the secondary compressed air exit comprised of a plurality of apertures. The plurality of apertures located at the secondary compressed air exit aims the secondary compressed air flow or second pattern into and about the first spray pattern of atomized coating particles traveling toward the workpiece, thus adding a boost of energy to the spray pattern. The boost of energy when added to the spray pattern encourages the atomized coating particles to hit and adhere to the workpiece. Additionally, the secondary compressed air flow leaving the attachment creates an directional flow of energy peripherally, which surrounds the pattern, corralling the atomized particles back into the spray pattern.
The spray attachment has the advantage which permits it's use with existing spraying devices and requires no special training for the operator. The spray attachment may be manufactured with different vane lengths as well as different canting angles at the distal end of the vanes giving the spray attachment the ability to be used with pre-existing atomizing spray devices. Additionally, the spray attachment may be used with, but is not limited to, any and all coatings, fluids, adhesives, paints, anti-corrosive agents, insecticides, herbicides, pesticides, waxes, fungicides and the like, which are currently employed to coat or be delivered to a workpiece or target area by a spray device. Such a device can be used by, but is not limited to use by, a human operator, a numerically controlled spray machine, a robotic spray device or the like. Such a device would substantially and measurably increase the transfer efficiency of the coating on the workpiece.
It is also noted that the invention can be employed with any spraying device. Additionally, the invention can be employed with airless atomization tools or air assisted airless atomization tools. Still, compressed air would be employed through the air pathways created by the invention when using such atomization spray devices.
The vane length is dependent on the nozzle of the spraying device which is employed with the invention. As different nozzles produce different spray patterns, the vanes will need to be adjusted in length accordingly in order to produce an air pattern which will add the boost or push to whatever may be spraying through the nozzle to increase the transfer efficiency to the target or workpiece.
The spray attachment will be discussed in further detail in the description in the Summary of the Invention and the Detailed Description of the Figures.
It to be understood that although the Figures show a conventional hand held spray gun, the invention is in absolutely no way limited to such a device. It may be employed with spray nozzles of any type, be they operated by humans, robots or machines, for cleaning, coating, cooling, drying, lubricating, dispensing, sanitizing, marking or other industrial processes and the like.